For quite a while there have been complaints about the starting locations for races being too close together.  I  have experienced this many times myself.  In version 3.03 changes were made that were supposed to keep the starting locations from being too close together.  I don't think they work as well as they should.  There are still complaints about the spacing with the new values.  I recently had a start with 2 races only separated from me by one star.

I have been trying many new values for the parameters that control the spacing and have finally found what I think are values that keep the starting locations as far apart as possible.  They are not equally spaced, but they are not very close together.  This depends on the number of races in the galaxy, but it works well for the recommended number.  I have tested many, but not all, combinations of galaxy size and type.

The new values I am using are:
    <PlayerStartSpacingWideMod>0.35</PlayerStartSpacingWideMod>
    <PlayerStartSpacingNarrowMod>0.175</PlayerStartSpacingNarrowMod>

This mod will not work with mods that change the GalCiv3MapDefs.xml file, since that is the one this mod changes.  The only mod that I know changes this file is Horemvore's UCP mod. 

Note to Horemvore: If you think these values do a good job of keep the starts apart, feel free to use them in your mod.

Note to Stardock: If you think these values do a good job of keep the starts apart, I hope you will put them into the game so there will be no need for this mod.

The mod is available here.